Software Defined Radio System Research Articles

Реалізація алгоритму пошуку кореляційного інтерферометричного пеленгатора засобами програмної платформи GNU радіо

In the realm of modern radio equipment development, the integration of Software Defined Radio (SDR) systems, encompassing both software and hardware components, has become widespread. SDR systems, particularly, find applications in the creation of direction finders for radio signal sources. The effectiveness of direction finding and the identification of radio radiation sources largely hinge on the technical specifications of the equipment. For contemporary systems aimed at detecting the location of radio radiation sources, direction finders based on a correlation interferometer prove to be highly suitable. These direction finders excel in performing direction finding for a wide array of radio signals, capable of recognizing broadband modulated signals. They can simultaneously process and identify several signals within a single frequency channel, originating either from a singular source of radio signals (coherent) or from multiple sources (incoherent). SDR technology enables programmable reconfiguration of a radio receiver through software. Such receivers boast a broadband radio frequency component with a significant dynamic range, a high-speed Analog-to-Digital Converter (ADC) path, a robust signal processor, and a specialized digital filtering path. SDR receivers are adaptable to signals of various standards and frequencies, depending on the specific tasks at hand. The GNU RADIO software platform stands out as the most flexible open-source software platform for SDR systems. This article delves into the utilization of the GNU RADIO software platform to implement the search algorithm for the direction finder of the correlation interferometer. The Ettus USRP N210 SDR platform was selected for implementing the direction finder using the correlation interferometer algorithm. This study introduces a two-channel software-controlled model of the direction finder, operating according to the correlation interferometer algorithm. The measurement results for the placement angle of radio signal sources yielded an individual absolute error ranging from 2 to 4 degrees, with an average absolute error of about 3 degrees. These results are quite commendable for such mobile two-channel systems. While systems with four or more channels boast higher accuracy, they tend to have lower economic feasibility.

Using Software-Defined radio receivers for determining the coordinates of low-visible aerial objects

The object of this study is the process of determining the coordinates of low-visible aerial objects. The main hypothesis of the research assumed that the signals emitted by airborne systems of airborne objects that are not visible to radar stations have a greater power than the signal reflected from the airborne object. This, in turn, could improve the signal/noise ratio and, accordingly, the accuracy of determining the coordinates of low-visible aerial objects. It is suggested to use Software-Defined Radio receivers to receive such signals emitted by on-board systems of low-visible aerial objects. It was established that the main sources of signals for Software-Defined Radio receivers are signals of command, telemetry, target channels, manual control channels, and satellite navigation. It was established that an additional distinguishing feature when determining the coordinates of low-visible aerial objects is the uniqueness of their spectra and spectrograms. The method of determining the coordinates of low-visible aerial objects when using Software-Defined Radio receivers has been improved, which, unlike the known ones, involves: – the use as signals for Software-Defined Radio of signal receivers of on-board equipment of low-visible aerial objects; – the use of a priori coordinate values of a low-visible aerial object; – conducting additional spectral analysis of signals of on-board systems of low-visible aerial objects. The spectra and spectrograms of signals of on-board systems of aerial objects when using non-directional and directional antennas were experimentally determined. The experimental studies confirm the possibility of using the Software-Defined Radio receiver to receive signals from airborne equipment and improve the signal-to-noise ratio. The accuracy of determining the coordinates of aerial objects when using Software-Defined Radio receivers was evaluated. A decrease in the error of determining plane coordinates by the Software-Defined Radio system of receivers compared to the accuracy of determining coordinates by the P-19 MA radar station was established by an average of 1.88–2.47 times, depending on the distance to the aerial object

Beam Squint in Ultra-Wideband mmWave Systems: RF Lens Array vs. Phase-Shifter-Based Array

In this article, we discuss the potential of radio frequency (RF) lens for ultra-wideband millimeter-wave (mmWave) systems. In terms of the beam squint, we compare the proposed RF lens antenna with the phase shifter-based array for hybrid beamforming. To reduce the complexities for fully digital beamforming, researchers have come up with RF lens-based hybrid beamforming. The use of mmWave systems, however, causes an increase in bandwidth, which gives rise to the beam squint phenomenon. We first find the causative factors for beam squint in the dielectric RF lens antenna. Based on the beamforming gain at each frequency, we verify that, in a specific situation, RF lens can be free of the beam squint effect. We use 3D electromagnetic analysis software to numerically interpret the beam squint of each antenna type. Based on the results, we present the degraded spectral efficiency by system-level simulations with 3D indoor ray tracing. Finally, to verify our analysis, we fabricate an actual RF lens antenna and demonstrate the real performance using a mmWave, NI PXIe, software-defined radio system.

Crypto coding system based on the turbo codes with secret keys

In 1997, the US National Science Foundation recognized the need to unite research communities together to solve mutual problems, overcome challenges, future development and practical applications of cryptography and error correction coding. Recent works in this area are connected with turbo codes, which have a special ability to provide error correction characteristics of the information transmission close to theoretically obtained values. Besides, they are used for television (DVB-RCS, DVB-RCT), wireless local networks (WiMAX), software-defined radio systems, mobile (3G, 4G, Inmarsat) and space (CCSDS) communications etc. In this article is presented the crypto coding system based on turbo codes with secret keys used by interleavers. All calculations are performed during data encoding, which reduces the computational complexity of data pre-encryption. The necessary mathematical apparatus was presented, the security level of the communication system was estimated, a simulation of the error correction characteristics was performed, and multimedia information was processed. The working characteristics of the classical and proposed turbo codecs do not differ statistically. The results can be used in communication systems for various functional purposes.

ALGORITHM FOR APPLICATION OF INFORMATION FOR MANAGEMENT OF USERS SPATIAL DISPOSITION IN THE PROCESS OF AUTOMATED SOFTWARE-DEFINED RADIO COMMUNICATION NETWORK IMPLEMENTED BY ORTHOGONAL FREQUENCY DIVISION AND MULTIPLEXING

A software-defined radio (SDR) system is a radio communication system which uses software for the modulation and demodulation of radio signals. An SDR performs significant amounts of signal processing in a general purpose computer, or a reconfigurable piece of digital electronics. SDR can talk and listen to multiple channels at the same time, also it can be quickly and easily upgraded with enhanced features. In fact, the upgrade could be delivered over-the-air In the long run, SDR is expected to become the dominant technology in radio communications

A seamless software defined radio development flow for waveform and prototype debugging

With the increasing number of wireless communication standards flexibility has gained more and more importance which has lead to the software defined radio (SDR) concept. However, SDR development has to face many challenges, among them are the questions how SDR systems can be designed to achieve flexibility, architectural efficiency, energy efficiency and portability at the same time. These requirements result in very elaborate architectures and a highly increased design complexity. To cope with such complexity, we proposed an SDR development flow. During the development of such SDR, debugging becomes more efficient on a prototype hardware implementation than on a simulation model. However, error analysis on a prototype suffers from strong limitations like a reduced state visibility. In this paper, an extension to the SDR development flow is presented and successfully applied to an example SDR. It allows for an efficient error analysis with the SDR simulation model by the feedback of stimulus data from the prototype.

Software-Defined Radio-Based Contactless Localization for Diverse Human Activity Recognition

This paper presents a study on contactless localization for activity recognition based on radio-frequency sensing. The focus of this study is on the quantitative analysis of the collected data, which is in the form of channel state information (CSI). The proposed method utilizes a software-defined radio (SDR) system in combination with an ensemble learning technique to localize and identify daily living activities such as leaning, sitting, standing and walking. Specifically, SDR device, Universal Software Radio Peripheral (USRP) models X300/X310 are utilized to collect data on the aforementioned activities. The data is collected from an empty space and a participant performing daily living activities in different territories. The acquired data is labelled based on the region, zone and performed activity. The CSI data is subsequently preprocessed and fed into an ensemble-based machine learning algorithm for classification. Furthermore, the stability analysis of the proposed method is performed to evaluate its reliability and robustness. The performance of the algorithm is evaluated using various metrics, including a confusion matrix, accuracy, cross-validation score and training time. The results demonstrate that the proposed ensemble-based approach achieves a high accuracy of up to 90% in activity recognition, highlighting the effectiveness of the proposed method in contactless localization for activity recognition.

Perturbations in the characteristics of ionospheric HF radio waves during the April 11, 2019, earthquake in Japan: Results from oblique sounding

The Harbin Engineering University HF software-defined radio system since 2018 continuously monitors dynamic processes launched in the ionosphere by energetic events in the Sun–interplanetary-medium–magnetosphere–ionosphere–subsystem coupling. The data collected during the submarine magnitude 6.0 earthquake that occurred off the East coast of Honshu, Japan, on April 11, 2019, have been analyzed with the specific objectives of determining the ionospheric response to the earthquake, the distortions of the radio-wave propagation channels, and identifying possible mechanisms for the transport of the disturbances at 845–2,260 km great-circle distances between the epicenter and the propagation path midpoints. Despite the ionospheric responses to powerful earthquakes have been studied since 1964, the problem of deriving global specifications of the disturbances remains pressing. The effects that the ionospheric disturbances from earthquakes have on radar, communications channels, radio navigation, radio astronomy, etc., are a matter of even greater urgency. The multiple path multifrequency radio system for sounding the ionosphere at oblique incidence provides a convenient tool for diagnosing such HF radio-wave propagation problems, acquiring a database containing the complex amplitudes of the signals and used to produce a sequence of Doppler spectra, for the first time, at a rate of 480 spectra per 1 h along 14 radio-wave propagation paths simultaneously with a 7.5-s temporal resolution and 0.02-Hz Doppler resolution over 20-s intervals. Analysis of the Doppler spectra, Doppler shift along the main ray, and signal amplitudes on the day when the earthquake occurred and on quiet time reference days showed that after the earthquake the Doppler spectra exhibit essential broadening, the Doppler shift along the main ray undergoes alternating sign Doppler variations, as well as quasi-sinusoidal variations with 3–5- and 10–20-min periods pertaining to the infrasound and atmospheric gravity wave frequency bands. The relative amplitudes of disturbances in the electron density are estimated to be ∼1% and 2–19% in the fields of infrasound of atmospheric gravity waves, respectively.

Resilient Embedded Systems Designs via on the Fly Generation of Adaptive Degenerate Components Using Machine Learning

Software defined radio (SDR) provides significant advantages over traditional analog radio systems and are becoming increasingly relied on for “mission critical” applications. This along with risk of trojans, single-event upsets and human error creates the necessity for fault tolerant systems. Redundancy has been traditionally used to implement fault tolerance but incurs a substantial area overhead which is undesirable in most applications. Advancements in field-programmable gate array and system on a chip technologies have made implementing machine learning (ML) algorithms within embedded systems feasible. In this paper we explore the use of ML to implement fault tolerance in an SDR. Our approach, which we call adaptive component-level degeneracy (ACD), uses a ML model to learn the functionality of an SDR component. Once trained, the model can detect when the component is compromised and mitigate the issue with its own output. We demonstrate the ability of our model to learn multiple simulated SDR components. We compare the one-dimensional convolutional neural network and bidirectional recurrent neural network architectures at modeling time series components. We also implement ACD within a real-time SDR system using GNU Radio Companion. The results show great potential for the utilization of ML techniques for improving embedded system reliability.

Effects of the super-powerful tropospheric western Pacific phenomenon of September–October 2018 on the ionosphere over China: results from oblique sounding

Abstract. Doppler measurements at oblique propagation paths from the city of Harbin, the People's Republic of China (PRC), to 10 high-frequency (HF) radio broadcast stations in the PRC, Japan, Mongolia, and the Republic of Korea captured the response in the ionosphere to the activity of the super typhoon, Typhoon Kong-rey, from 30 September to 6 October 2018. The Harbin Engineering University coherent software-defined radio system generates the database containing the complex amplitudes of the radio signals that have been acquired along 14 propagation paths since 2018. The complex amplitudes are used for calculating the temporal dependences of the Doppler spectra and signal amplitudes, and the Doppler spectra are used to plot the Doppler shift as a function of time, fD(t), for all rays. The scientific objectives of this study are to reveal the possible perturbations caused by the activity of Typhoon Kong-rey and to estimate the magnitudes of wave parameters of the ionospheric plasma and radio signals. The amplitudes, fDa, of the Doppler shift variations were observed to noticeably increase (factor of ∼2–3) on 1–2 and 5–6 October 2018, while the 20–120 min periods, T, of the Doppler shift variations suggest that the wavelike disturbances in the ionosphere are caused by atmospheric gravity waves. The periods and amplitudes of quasi-sinusoidal variations in the Doppler shift, which have been determined for all propagation paths, may be used to estimate the amplitudes, δNa, of quasi-sinusoidal variations in the electron density. Thus, T≈20 min and fDa≈0.1 Hz yield δNa≈0.4 %, whereas T≈30 min and fDa≈0.2 Hz give δNa≈1.2 %. If T≈60 min and fDa≈0.5 Hz, then δNa≈6 %. The periods T are found to change within the 15–120 min limits, and the Doppler shift amplitudes, fDa, show variability within the 0.05–0.4 Hz limits.

Bandpass Sigma–Delta Modulation: The Path toward RF-to-Digital Conversion in Software-Defined Radio

This paper reviews the state of the art on bandpass ΣΔ modulators (BP-ΣΔMs) intended to digitize radio frequency (RF) signals. A priori, this is the most direct way to implement software-defined radio (SDR) systems since the analog/digital interface is placed closer to the antenna, thus reducing the analog circuitry and doing most of the signal processing in the digital domain. In spite of their higher programmability and scalability, RF BP-ΣΔM analog-to-digital converters (ADCs) require more energy to operate in the GHz range as compared with their low-pass (LP) counterparts. This makes conventional direct conversion receivers (DCRs) the commonplace approach due to their overall smaller energy consumption. This paper surveys some circuits and systems techniques which can make RF ADCs and SDR-based transceivers more efficient and feasible to be embedded in mobile terminals.

A Top-Down Modeling Approach for Networks-on-Chip Components Design: A Switch as Case Study

The design of Networks-on-Chip (NoCs) components implies a wide range of techniques and methods to address the microarchitecture of the packet-forwarding components, where routers and switches are the most complex because they constitute the NoC’s backbone. Due to this complex design space, several works use approaches limiting architectural exploration, focusing only on achieving high-performance levels; therefore, they are inadequate for designing NoC components when particular functionalities are demanded, as in real applications with specific protocols and interfaces. This paper presents a design methodology based on a top-down approach with NoC-oriented abstraction levels to systematically generate a microarchitecture and its hardware description according to system requirements. The design flow transforms a high-level functional model into a microarchitecture model through a refinement process at each abstraction level. This structured approach involves integrating details on how the data is functionally managed within the component according to the system requirements and the processing granularity of each level, allowing testing alternatives in the early stages of the design when necessary. The models of each abstraction level can be described and simulated using the simulator OMNet++. Thus, the obtained microarchitecture model will be directly translated into a Hardware Description Language (HDL). The methodology is tested via the design of a NoC switch for a Software Defined Radio (SDR) system. Performance analysis and implementation results in a field-programmable gate array (FPGA) show that the proposed design is functional and comparable in both area and frequency to other similar state-of-the-art components, and it is also configurable to build star topologies of up to 16 nodes.

Development of a Bench for Analyzing the Radio Station Operation in the APCO P25, DMR and TETRA Communication Standards Based on Broadband Software-Defined Radios and GNU Radio Software Toolkit

The article discusses the development of an instrument complex (bench, stand) for the study of digital radio communication standards: APCO P25, DMR and TETRA, based on software-defined radio systems (SDR) technologies in voice mode. The bench is based on the HackRF One broadband SDR transceiver and the GNU Radio open software toolkit. Along with the SDR transceiver HackRF One, it is proposed to use the SDR TV tuner AstroMeta Digital TV Dongle as an available receiver. The structure of the hardware and software parts of the bench is proposed. The software implementation of listed digital radio communication standards is based on the open libraries of the Osmocom project: the BoadBot OP25 and TETRA Live Monitor libraries. The operating system Linux Debian 10 and the software toolkit GNU Radio 3.7 were used for practical testing of the bench functioning. The practical testing results of the developed bench are presented both when interacting in voice mode with radio stations of the specified radio communication standards, and between the SDR transmitter HackRF One and the SDR TV tuner AstroMeta Digital TV Dongle. For the radio communication standards APCO P25 and DMR, the receiving and transmission modes of the speech signal have been practically tested on the developed bench, and for the radio communication standard TETRA, the modes of scanning the radio broadcast and receiving the speech signal have been tested. As a bench operability confirmation for the listed radio communication standards, the screenshots of programs implementing the specified modes of interaction between the bench hardware components are given. The proposed bench architecture allows to expand the list of supported radio standards. The developed bench can be used: 1) for educational purposes in the study of radio communication standards; 2) in the development and debugging of radio communication systems under development; 3) for control testing during the release of radio systems.

Design and Development of an FPGA Board for Software-Defined Radio Research

This paper describes the design and development of a cost-affordable yet powerful software-defined radio system. The main application environment of the board is in academia where it is used to deliver a multidisciplinary approach in a number of fundamental engineering topics in communications. A moderately fast ADC together with an audio DAC are used for the analog components while an off-the-shelf FPGA is used as the digital processing element. To demonstrate the boards capabilities, hardware blocks to demodulate amplitude modulation and digital modulation were developed.

ОБЗОР ИСТОЧНИКОВ ПОМЕХ В СПУТНИКОВЫХ СИСТЕМАХ СВЯЗИ

The article discusses some sources of interference in satellite communication channels, such as the impact of the ionosphere, space weather and the impact of man-made sources of interference. It is shown that satellite information transmission systems remain relevant and continue to develop, plans and projects for the further development of this type of communication in the Russian Federation are also considered. The relevance of VSAT systems and the scope of their current application are considered, as well as possible ways of using this type of satellite communication are proposed, the main methods of application are monitoring systems and communications in remote places of our planet, as well as the study of space and monitoring the state of satellite repeaters located in outer space. The advantages and disadvantages of building such systems are analyzed, and the idea of leveling the emerging shortcomings by using cognitive radio technologies using the capabilities of software-defined radio systems is proposed.

Progress of the ECHo SDR Readout Hardware for Multiplexed MMCs

The electron capture in ^{163}Holmium (ECHo) experiment seeks to achieve sub-eV sensitivity of the electron neutrino mass through calorimetric decay spectroscopy of ^{163}Ho in large arrays of cryogenic magnetic microcalorimeters (MMCs). Microwave SQUID multiplexing serves to efficiently increase the number of readout channels, thus calorimeters per array and ultimately per cryostat. A corresponding frequency multiplexing room temperature software-defined radio (SDR) system is in development to enable the readout of this increased number of MMCs per cable. The SDR consists of a custom FPGA platform that provides signal generation and analysis capabilities, as well as tailored signal conversion and analog conditioning front end electronics that enable the room-temperature-to-cryogenic interface. Ultimately, the system will read out 400 multiplexer channels with double pixel detectors through a bandwidth of 4 GHz (IEEE C band). As high-resolution data converters are limited in sample rate, the C-band is split into five sub-bands using a two-stage mixing method. In this contribution, a prototype of the heterodyne RF design is presented. It comprises one of the five 800 MHz sub-bands for a target frequency range between 4 and 8 GHz. Furthermore, the second version of the A/D converter stage is presented, capable of generating and digitizing up to five complex basebands using 1 GSs^{-1} converters, the reference clocks and a flux-ramp signal. We will show first results of their single and combined characterization in the lab. The current state of the prototype hardware enables preliminary measurements, only limited in bandwidth and with slightly higher noise. Potential improvements could be derived and will be implemented in the full bandwidth, 5-sub-band RF PCB design.

On the use of high-frequency surface wave oceanographic research radars as bistatic single-frequency oblique ionospheric sounders

Abstract. We demonstrate that bistatic reception of high-frequency oceanographic radars can be used as single-frequency oblique ionospheric sounders. We develop methods that are agnostic of the software-defined radio system to estimate the group range from the bistatic observations. The group range observations are used to estimate the virtual height and equivalent vertical frequency at the midpoint of the oblique propagation path. Uncertainty estimates of the virtual height and equivalent vertical frequency are presented. We apply this analysis to observations collected from two experiments run at two locations in different years, but utilizing similar software-defined radio data collection systems. In the first experiment, 10 d of data were collected in March 2016 at a site located in Maryland, USA, while the second experiment collected 20 d of data in October 2020 at a site located in South Carolina, USA. In both experiments, three Coastal Oceanographic Dynamics and Applications Radars (CODARs) located along the Virginia and North Carolina coast of the US were bistatically observed at 4.53718 MHz. The virtual height and equivalent virtual frequency were estimated in both experiments and compared with contemporaneous observations from a vertical incident digisonde–ionosonde at Wallops Island, VA, USA. We find good agreement between the oblique CODAR-derived and WP937 digisonde virtual heights. Variations in the virtual height from the CODAR observations and the digisonde are found to be nearly in phase with each other. We conclude from this investigation that observations of oceanographic radar can be used as single-frequency oblique incidence sounders. We discuss applications with respect to investigations of traveling ionospheric disturbances, studies of day-to-day ionospheric variability, and using these observations in data assimilation.

Eğitsel SDR Tekniklerine Dayalı FPGA Tabanlı FM Radyo Verici Tasarım ve Uygulaması

The basic purpose of Software Defined Radio (SDR) systems is to use a digital signal processor to numerically handle radio signals. The use of a processor like a Field Programmable Gate Array (FPGA) to perform tasks like modulation, demodulation, signal creation, and line coding on these systems dramatically decreases the demand for analog circuit-based hardware. FPGAs are digital integrated circuits with a wide range of applications which are made up of links between programmable logic blocks. It's aimed at assisting the creator realize the logic functions that the designer needs. In consequence, the user may change the function of each logic block. VHSIC Hardware Description Language (VHDL) is commonly used in FPGA programming. In this study, VHDL code was created, and a FM transmitter was implemented on a FPGA board (CMOD A7) in this research. The sound card interface on the PC used to send and receive the signals while suitable ADC and DAC cards are used on the FPGA side for the same purpose. Audacity program was used to playback the sample wav files while HDSDR SDR program was used to monitor and record the signals in wav file format. Finally, using the MATLAB code, the recorded transmitter signal was demodulated offline, and the output was stored to the hard drive. The demodulated signal obtained is identical to the initial modulation signal, indicating that the modulation was correctly executed. As a result, a perfect foundation for the development and training of SDR systems using FPGA has been established.

GNSS Time Signal Spoofing Detector for Electrical Substations

This paper introduces a novel method of GNSS spoofing detection with applications in electrical substations. Time sensitive applications in electricity substations, including Phasor Measurement Units (PMU) and Merging Units (MU), rely on Global Navigation Satellite Signals (GNSS), often GPS, for time transfer. Recently, sophisticated ‘spoofing’ attacks have become feasible due to the availability of low cost Software Defined Radio (SDR) systems. The proposed method uses multiple GNSS receive antennas placed in close proximity at the electricity substation, such that it is not possible for an attacker to target a unique spoofing signal towards each antenna. In a system employing three or more receive antennas, during a spoofing attack two or more of the GNSS receive antennas will return an estimated position in impossible locations. This is sufficient to raise alarm that time sensitive applications should use an alternative time source or holdover clock. The contributions of this paper include a detailed description of the proposed method, an experimental assessment of GNSS receiver and substation clock position estimation variance to establish the minimum separation required between receive antennas, and a validation of the method by experimental demonstration. A further benefit of the authors’ method is that it may be put into practice immediately using commercial-off-the-shelf (COTS) substation clock equipment.

AI-Managed Cognitive Radio Digitizers

Embedding Artificial Intelligence (AI) in integrated circuits is one of the technology pillars of the so-called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">digital transformation</i> . Nowadays, the vast majority of electronic devices benefits from digital signal processing to implement more and more functionalities, which can be further enhanced by the action of AI algorithms and artefacts. Moreover, as the analog/digital interfaces are moving closer and closer to the point where the information is either acquired or transmitted, the so-called AI-managed data converters are becoming key building blocks in an increasingly number of interconnected <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cyberphysical</i> systems–made up of both software and hardware components. Software Defined Radio (SDR) and Cognitive Radio (CR) systems intended for 5G/6G communications are good examples which can benefit from an early digitization managed by AI engines. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this context, this paper presents an overview of circuits and systems techniques for AI-managed analog/digital interfaces with application in SDR/CR mobile telecom systems. Some design trends and challenges are discussed, going from new communications and computing paradigms for AIoT devices and networks, to digital-based/scaling-friendly analog circuit techniques for an efficient digitization. The state of the art on Analog-to-Digital Converters (ADCs) is surveyed, putting emphasis on highly-programmable Sigma-Delta Modulators (<inline-formula><tex-math notation="LaTeX">$\Sigma\Delta$</tex-math></inline-formula>Ms) as one of the best ADC candidates for SDR/CR transceivers. Some chip examples are shown to illustrate their potential application in AI-enhanced CR end-devices.